Among benzonaphthacene glycosides, for example, some of pradimicin antibiotics and semi-synthesized derivatives thereof bind to cells as targets that express mannan having D-mannose residues on cell surface layers, and have been considered promising, for example, as candidate compounds for antifungal agents. Reviews are available which summarize the correlation between the structures and antimicrobial activity of these compounds (see, for example, Non-patent document 1 mentioned below). Among variety of homologues or derivatives thereof, BMY-28864 (or N,N′-dimethylpradimicin FA-2) has been reported as a semi-synthesized derivative having superior water solubility and potent antimicrobial activity (see, for example, Non-patent document 2 mentioned below). Furthermore, pradimicin T1 comprising the benzo[α]naphthacenequinone skeleton bound with D-xylose at the 11-position has also been reported (see, for example, Non-patent documents 3 and 4 mentioned below).
However, any development of these compounds as medicaments has not yet been succeeded to date. Major presumable reasons include, for example:    i) these compounds have high self-aggregational property and therefore likely incorporate impurities in a culture medium (lipopolysaccharides and the like), and such impurities may possibly exhibit toxicity;    ii) solubilities of compounds as candidates for development in biological fluids (blood and the like) are still far from satisfactory, which results in insufficient kinetics in vivo such as poor absorption or clearance.    [Non-patent document 1] Oki, et al., Exp. Opin. Ther. Patents, 4(12):1483-1491 (1994)    [Non-patent document 2] Oki, et al., J. Antibiotics, 43, 1230-1235 (1990)    [Non-patent document 3] Furumai et al., J. Antibiotics, 46, 589-597 (1993)    [Non-patent document 4] Hasegawa et al., J. Antibiotics, 46, 598-605 (1993)